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Nuclear Cardiology > Physics > Flashcards

Physics Flashcards

1
Q

1mCi=

A

37 MBq

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2
Q

Auger effect

A

When electron drops a level to fill a sudden vacancy energy is not emitted but transmitted to another electron ejecting it too - AUGER ELECTRON

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3
Q

Characteristic X-rays

A

Occur when an inner shell electron is ejected and its vacancy is filled by another electron

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4
Q

Curie (Ci)

A

Radioactivity - disintegrations per second 1mCi=37MBq

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5
Q

Roentgen

A

Radioactivity exposure - radiation in environment

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6
Q

Gray (Gy)

A

Radiation dose

1 Gy=100 RAD

(Radiation Absorbed Dose)

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7
Q

REM

A

Radiation absorbed by tissue

(Radiation Equvalent Man)

100 RAD=100 REM=1 Sv

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8
Q

Z

A

Atomic number (# protons)

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9
Q

A

A

Atomic mass

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10
Q

201Tl energy emssion

A

80 keV mercury X-rays

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11
Q

99mTc energy emission

A

140 keV gamma

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12
Q

17 segment model

A
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13
Q

Recombination zone

in gas-filled detector

A

unusable – higher probability of recombination of ion pairs than their detection

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14
Q

Geiger-Mueller counter

A

* output independent of absorbed energy

* used for survey meters

* 10x more sensitive than ion chamber

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15
Q

NaI scintillator

A
  • dense – good absorber of gamma-rays
  • efficient scintillator – 30 photons/keV
  • light output proportional to amount radiation absorbed
  • very fragile
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16
Q

Gamma camera energy resolution at 140 keV

A

9-11%

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17
Q

FWHM

A

Full width at half maximum – curve spread at the location 50% down on each side from peak amplitude

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18
Q

Collimator

A

Septa between holes absorb photons travelling in oblique lines so they never strike the detector

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19
Q

Gamma-camera ENERGY correction

A
  • Decreases the system’s FWHM
  • improves contrast (ability to resolve 2 points in space)
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20
Q

Gamma-camera LINEARITY correction

A
  • PMT has a non-linear response to light across its face
  • increased sensitivity at edges compared to center
  • consequently, events at edges are misposition toward the center of the PMT
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21
Q

Gamma-camera UNIFORMITY correction

A
  • aquire a high-count flood
  • measure the average counts per pixel
  • for each pixel compute a correction factor
  • store corrections as a uniformity correction map
  • correct clinical studies by multiplying each pixel in the image by its corresponding factor from the map
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22
Q

Parallel-hole collimator response to radiation

A
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23
Q

Collimator specs

A

1) energy (keV);
* thinkness of septa and materials used*
2) spacial resolution
* FWHM of 1 mm pint source @ 10 cm away*
3) sensitivity
* CPS/mCi (counts/second/radiation)*

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24
Q

Parallel-hole collimator design

A
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25
Q

System resolution

A

Rs2=Rc2 + Ri2

Rc (collimator) ~ 8 mm

Ri (instrinsic) ~ 3 mm

Rs (system) ~ 8.5 mm

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26
Q

Effect of source to collimator distance

A

Degrades resolution but not sensitivity

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27
Q

Non-standard collimators

A
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28
Q

New design collimators

A
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29
Q

Angular sampling

A

How many projections

(recommended # is 64)

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30
Q

Star artifact

A
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31
Q

Filtered backprojection

A

Mathematical filter to remove star artifact

(RAMP FILTER)

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32
Q

Point response function

A
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33
Q

RAMP artifact

A
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34
Q

FREQUENCY DISTRIBUTION

in SPECT imaging

A

low frequency = gross objects

mid frequency = detail + noise

high frequency = noise + detail

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35
Q

Effect of UNDERFILTERING

A
  • can create lesions
  • cut-off frequency set too high
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36
Q

Effect of OVERFILTERING

A
  • can mask a lesion
  • cut-off frequency set too low
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37
Q

ISOBARS

A

isobar – equal “a” nucleons

9943Tc and 9942Mo

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38
Q

ISOTOPES

A

Isotopes - Equal Protons (z)

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39
Q

ISOTONES

A

Isotones - Equal neutrons (a - z)

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40
Q

ISOMERS

A

Isomers – same radionuclide, but different energy state

99mTc (metastable) and 99Tc

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41
Q

BETA- emission

A
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42
Q

BETA+ emission

A
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43
Q

ELECTRON CAPTURE

A
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44
Q

admissible 99Mo breakthrough

A

<0.15 uCi/1 mCi Tc (at time of dose administration)

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45
Q

Aluminum +++

admissible impurity level

A

<10 PPM

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46
Q

admissible HRTC (hydrolyzed reduced Technetium)

A

<2%

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47
Q

Effective t1/2 formula

A

1/effective half-life = 1/biologic half-life + 1/radioactive or physical half-life.

48
Q

Physical t1/2 formula

A

Physical t ½ = 0.693/x (decay constant)

49
Q

Technetium production/decay

A

Production: Reactor → Generator (parent 99Mo)

Decays: Gamma decay

50
Q

Thallium production/decay

A

Production: Cylcotron (parent 201Pb)

Decays: Electron capture (decays to 201Hg)

51
Q

18-FDG production/decay

A

Production: Cyclotron

Decays: Beta + decay (Positron)

52
Q

STOCHASTIC

A

Stochastic (probabilistic)

The probability, not severity, of occurrence increases with dose

  • Severity is not related to magnitude of dose
  • No threshold dose
  • Any dose is assumed to carry some risk
53
Q

DETERMINISTIC

A

Non-stochastic (deterministic)

Severity of ailment increases with dose

  • Known threshold dose of disease induction
  • Severity increases above that threshold
  • Examples: Skin injury, cataract formation
54
Q

background radiation exposure values

A

~360 mRem/year (1 mRem/day)

~300 from natural

~60 from artificial sources

55
Q

maxiumum allowed radiation exposure

A

RADIATION WORKERS: 5 Rem/year

56
Q

Meds that inhibit binding of the Tc-99 pertechnetate to the hemoglobin

A
  • hydralazine
  • prazosin
  • heparin
  • digoxin
57
Q

LVEF by ERNA

*equilibrium radionuclide angiocardiography *

A

LVEF = Background corrected end diastolic counts – Background corrected end systolic counts/ Background corrected end diastolic counts

58
Q

LEHR Collimator efficiency

A

1:10,000 (0.01% )

59
Q

How often to check

frequency of energy peaking for a gamma camera?

A

daily

60
Q

PMT structure

A
61
Q

Image reconstruction process flow

A

Thirty-two to sixty-four planar projections are acquired 180 degrees around the patient perpendicular to the long axis of the body, and the initial reconstruction is into the transaxial plane. From these transaxial images, the long axis of the heart is defined, and subsequently the conventional vertical and horizontal long-axis and the short-axis images are reconstructed for analysis.

62
Q

SPECT image aquisition flow

A

In a cardiac SPECT study, typically 64 projections are obtained over 180 degrees at 3- degree increments, and each projection usually takes about 20 seconds.

63
Q

LET

A

amount of energy deposited per length of absorber

(keV/um)

electomagnetic and beta- have low LET

alpha- have high LET

64
Q

Using AC and resolution compensation

A

Reduces number of false positives

65
Q

Rubidium-82 source

A

Rubidium-82 is the daughter of strontium-82 (half-life = 25 days) and is eluted from a strontium-82/ rubidium-82 generator. The other PET agents are produced in medical cyclotrons.

66
Q

Caution: High Radiation Area sign

A

NRC regulation states that when an individual could receive a dose > 500 rads per hour at 1 m from the source, area should have the “Caution: High Radiation Area sign posted”.

67
Q

Transportation index

A

Exposure measurement at 1 m from the surface of the package.

68
Q

Well counter

A

A well counter is a device used for measuring radioactivity in small samples. It usually employs a sodium iodide crystal detector. It was invented in 1951 by Hal Anger, who is also well known for inventing the scintillation camera.

69
Q

MAX dose to fetus

A

500 mrem

70
Q

Effect of LVH on SPECT images

A

LVH may improve count statistics, which results in better-quality images with the risk of hiding small areas of ischemia.

71
Q

Effect of prone imaging

A

Prone imaging (patient lies on abdomen) provides greater separation between the heart and the diaphragm, so there is less inferior wall attenuation in comparison to a supine image (patient lays on back).

72
Q

ANEDONSINE receptors

A

A1 - AV node

A2A - target

A2B/A3 - bronchial

73
Q

DIPYRIDAMOLE

A

Dipyridamole is primarily metabolized in the liver and should be used cautiously in patients with hepatic dysfunction. The biologic half-life of dipyridamole is 30 to 45 minutes. Adenosine but not dipyridamole is rapidly taken up by red blood cells and endothelial cells, and this explains the short biologic half-life of adenosine. The longer half-life makes it a good agent for PET imaging as it does not need to be given.

74
Q

Why also exercise when giving vasodilators?

A

The patients usually undergo a low-level exercise without achieving target heart rate in order to minimize side effects of vasodilators and facilitate the clearance of tracer activity from the liver and gut

75
Q

Duke score

A

DTS = exercise time (in minutes) – [5 × (amount of ST-segment deviation in mm) – 4 × exercise angina index

76
Q

MPI sensitivity to detect obstructive CAD

A

85%

77
Q

LV dilation on SPECT without ischemia

A

hypertensive heart disease

78
Q

Intrinsic or extrinsic uniformity

A

daily

79
Q

Resolution and linearity

A

once a week

80
Q

center of rotation

A

once a month

81
Q

Collimator integrity

A

once a year

82
Q

test linearity of camera

A

four-bar phantom is placed between the cobalt-57 sheet and the collimator

83
Q

test intrinsic uniformity of system

A

remove collimator,

test with single 99mTc point source

84
Q

test extrinsic uniformity of system

A

planar sheet of 10-15 mCi of Co-57 is placed ON TOP OF COLLIMATOR

85
Q

Tc reduction

A

Technetium is eluted in the form of sodium pertechnetate via ion exchange with chlorine in the alumina column. In sodium pertechnetate, the oxidation state of technetium is +7, its most stable oxidation state. It is reduced to +5 and +4 before labeling.

86
Q

Increased levels of pertechnetate (99mTcO4-)

A
87
Q

99mTc-labelled macroaggregated albumin

A

99mTc-labelled macroaggregated albumin localizes predominately in the lungs and is used for lung perfusion.

88
Q

hydrolyzed reduced 99mTc

A

hydrolyzed reduced 99mTc as TcO2 or 99mTc-stannous colloid localize mainly in the liver

89
Q

1/2 life 15O

A

122 sec

90
Q

1/2 life 82Rb

A

75 sec

91
Q

1/2 life 18F

A

110 min

92
Q

1/2 life 123I

A

132 hous

93
Q

123I-MIBG

A

123I is used in the MIBG scan for patients with heart failure and has prognostic value. The cardiac sympathetic nervous system can be imaged noninvasively using 123I-MIBG tracer. The reduced heart-to-mediastinum (H/M) ratio uptake of123I-MIBG has been associated with worse cardiovascular outcomes, including ventricular arrhythmia and death.

94
Q

MISADMINISTRATION

A

Administering the wrong radiopharmaceutical to a person, by a route other than the route prescribed by the authorized physician, to a part of the body other than the part of the body specified by the authorized physician, a diagnostic dose of more than 50 mSv effective dose equivalent, and a therapeutic dose of more than 20% are all examples of misadministration.

95
Q

MISADMINISTRATION reporting

A

The NRC, not the FDA, should be informed about the misadministration of a radioactive tracer. The NRC must be notified by the next calendar day by telephone after the misadministration, and a written report must be submitted no later than 15 days after the event.

96
Q

Cardiotoxicity by MUGA

A

LVEF decreased by 10% and is lower than 50%

97
Q

Only technique that quantifies RV

A

Gated blood pool SPECT

but NOT

First-pass ventriculography

98
Q

Minimum counts per pixel

A

A minimum of 200 counts/ pixel using technetium-99m and 100 counts/ pixel using thallium-201 in the myocardium on an anterior projection is recommended.

99
Q

Off peak uniformity test

A
100
Q

What type of breathing is best when using CT for attenuation correction?

A

tidal breathing

101
Q

half value thickness (layer) for 99mTc photons in tissue

A

about the same as water

102
Q

Sinogram

A

A sinogram is a single row of pixels, repeated for each planar projection. Each sinogram is used to reconstruct a single transaxial slice.

103
Q

Alumina breakthrough from a 99mTc generator is evaluated by

A

Colorimetric test

104
Q

What is the main photon energy of 99Mo

A

740 and 780 Kev

105
Q

Caution, radioactive material

A
106
Q

Caution, radioactive material

A
107
Q

Caution, radiation area

A
108
Q

Caution, high radiation area

A
109
Q

Dose to organ limit (annual REM)

A
110
Q

Lens of the eye limit (annual REM)

A
111
Q

Extremity annual limit (REM)

A
112
Q

Skin annual limit (REM)

A
113
Q

member of public (annual REM)

A
114
Q

misadministration

A

AND >50 mSev total body

OR

> 0.5 Sev organ

115
Q

Limits fr DOT labelling

A
116
Q

11C-hydroxyephedrine

A

11C-hydroxyephedrine is used to depict sympathetic innervation of the myocardium.

117
Q

11C-acetate

A

11C-acetate is a marker of myocardial oxidative substrate metabolism.

Because 11C-acetate has a high first-pass myocardial extraction fraction, images obtained early following tracer injection can also be used to measure regional tissue blood flow,

Nuclear Cardiology (1 decks)

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